Mortared Stack Stone Wall

Mortared stack stone walls are lasting structures boasting strength and durability.

Download a PDF of our Mortared Stack Stone Wall Project Guide

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Project Photos

See the photos below for examples of finished projects. Click the thumbnails to view larger images.

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Required Tools

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Materials Needed

* Quikrete Mason’s Mix can be used in place of Type S mortar and Masonry Sand

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Coverage Calculations

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Preparation

  1. Please remember to call before you dig! Having to repair broken utilities will cost you more time and money then expected. In Georgia, call 1-800-282-7411 or visit www.gaupc.com
  2. Mark the proposed area to get proper measurements and a visual reference of where your wall will be installed.
  3. Measure the area. Reminder: When purchasing material account for at least 10% waste due to the shaping and cutting of the stone.
  4. Plan your drainage system when you plan for the wall. Keep in mind that mortared stack stone walls will not allow water to drain from behind the wall causing immense hydrostatic pressures and stresses to be placed on the wall. Too much pressure pushing on the back of the wall will cause a critical failure and destroy the wall.
  5. The height of the wall, what type of soil is present, what the wall is used for, and how well the surrounding landscape drains are all factors that will determine what size foundation is required.
    • Walls less than 3’ tall should be supported adequately by 4” of concrete under the ground level, 12” wide.
    • Walls over 3’ to 4’ tall should use at least 6” of concrete under the ground level, 18” wide.
    • If you plan on constructing a wall over 4’ tall, please do not use this guide. Walls over 4’ in height should be constructed using an engineer’s specifications, who has inspected the proposed construction site. Always check with the codes department of your local government before undertaking any project.

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Installation

  1. Remove the Soil where your wall will be built. It’s always a good idea to dig the foundation a little deeper so the first row of stone is partially buried under the ground. Remove the dirt behind the wall to account for your drainage system.
  2. Pouring the foundation. You can use bagged concrete mix for smaller projects or hire a concrete truck for larger ones. If you decide to do it yourself, this is where the concrete mixer comes in handy.
    • Before you pour concrete, be sure to compact the soil under the foundation.
    • You can add rebar and fiber mesh reinforcement for additional strength in the foundation.
    • The top surface of the foundation does not have to be perfectly smooth since it will be completely hidden from view.
    • The foundation does not have to be level. Some installers prefer that is level so they can use the block as a level reference when covering wall with stone.
  3. Laying Block. CMU Block or Concrete Masonry Unit Block is a manufactured concrete product designed to form load-bearing vertical surfaces such as foundation walls for houses, retaining walls and so forth. There are many installation techniques for this material. This guide will only briefly cover a simple installation option.
    • Once the foundation has set up (usually after 24 hours) you may start laying block.
    • Mortar: One 80 lb. bag of Type S mixed with 160 lbs. of masonry sand will cover 33 pieces 8” x 8” x 16” block. Or one bag of Quikrete Mason’s Mix will lay approximately 11 pieces 8” x 8” x 16” block.
    • Start at one end of the wall and place a trowel full of mortar onto the foundation where the block will be placed. For the first row of block it might take a little more.
    • Set the first row of block closer to the back of the foundation. Remember you will be adding 3” to 8” of mortar and stone to the front of the wall and this material needs to rest on the foundation as well.
    • Push the block down into the mortar tapping slightly with a hammer or trowel until mortar squishes out from under the block and you have achieved a 3/8” mortar joint. Be sure the block is level.
    • Place the block end to end along the first row making sure there is mortar under and between each block. Try to keep a consistent 3/8” joint.
    • Use the level to keep the block in check. You may have to add some mortar under a block to help level it.
    • If you are using weep holes for drainage you want the holes just above finished ground level. Notch out or drill holes through the block large enough to slide a section of pipe through. The pipe will have to extend past the block wall to the face of the stone. It is recommended to angle the pipes slightly down towards the face of the wall (higher at the back side of the wall) to ensure they drain properly.
    • Split a block in half so you have two pieces approximately 8” x 8” x 8”. Use this half block to start the next row. Doing this will ensure you have alternating vertical joints on the wall. This is important for the structural integrity of the wall.
    • As you add rows of block, place wall ties between the rows. Wall ties are later built into the stacked stone to keep the stone from separating from the front of the block wall.
    • Continue adding rows of block until you have reached the height desired.
    • For added strength, rebar and concrete can be used to fill the cells of the block. Rebar should also be tied into the foundation for additional support.
    • CMU Cap blocks can be used to add 2” to 4” to the wall to reach the finished height.
  4. Install the drainage next. There are many options when it comes to drainage. We will only cover the most commonly used method here.
    • Start by spreading granite 57 stone ~2” thick, behind the wall approximately 12” deep. This gravel bed should have a high end and gradually slope to a lower end. Another option is to make the highest point in the middle of the wall. This will allow the water in the drain pipe to flow in two directions. If possible have the water flow away from the house.
    • Lay a 4” diameter or larger perforated drain pipe on the gravel bed behind the wall. You can purchase this pipe with a silt filter preinstalled, called Sock Pipe. The low end of the pipe should exit out the side of the wall or out of the face of the wall.
    • Backfill the wall with granite 57 stone, 8” to 12” deep. Backfill up to the last 6” of the finished wall height. Top off the area behind the wall with top soil or mulch.
  5. A mason’s line can be used to help you keep the courses of stone level and to aid in finishing the wall so the top is level as well.
    • Place a stake in the ground at the start of the wall close to where the face of the wall will be. Attach the line to this stake close to where the second or third course of stone will be. Attach the other end of the line to another stake down the wall. Make sure the line is taut. If you have a curved wall you will have to place a couple of stakes to keep the line close to the wall, but not touching it.
    • Use a line level and attach it to the line. This level will help you make sure the mason’s line is level between the stakes.
    • Use the line as a reference point when stacking your stones. Run your courses of stone as close to the line as possible. Using a properly set up mason’s line will ensure you don’t have a crooked looking wall with dips and odd angles.
    • As you build up the wall, you will have to move up and re-level the mason’s line as you go.
  6. Installing the stone. This step will determine how the finished wall will look. The material chosen will play a major factor in the final outcome.
    • When placing the stone for the first row, use your trowel to lay a 1” bed of mortar under and 1” to 2” between the stone and the block wall. Press the stone firmly into place while wiggling it side to side and slightly rotating to ensure a good solid start. Use the rock hammer to tap each stone in place.
    • Once the stone is in place, you can fill the space between the back of the stone and the front of the block wall with mortar and small, scrap rock chips (if you are chipping and shaping the stone.) Some masons dispose of the chips by dropping them into the empty cells of the CMU block.
    • Make sure you break up the vertical joints through the wall. Long consecutive vertical joints can leave you with an eyesore and an unstable wall.
    • Don’t spend too much time on one piece. The rule of thumb is: “If you have to turn or flip the stone more than 3-4 times and it still does not fit, toss it to the side and try another.” It will fit somewhere else.
    • Constantly check the level of the stones with the torpedo level, and how level they are to each other with the 2’ or 4’ level. If you are using the mason’s line, be sure your courses are level with the line. If a stone is out of level you can always use a small stone shim or to level it up.
    • Reshaping some pieces of stone will be required. Use the rock hammer or stone saw to shape them to the desired contour.
  7. All walls constructed in this manor will need some sort of cap. Most caps use larger flat pieces that average 3” in thickness. Mortar the cap pieces in place leaving a 1” to 2” overhang off the front side of the wall.
  8. (optional) Grout the joints. You can dramatically change the look of a wall just by the grout technique used.
    • Dry Stack: The mortar is only on the back of the stones and does not show on the face at all. This can be a lot of work because each stone must fit perfectly together to avoid gaps where mortar could be seen.
    • Raked Joint: Similar to how the majority of joints are done for brick. A joiner tool is used in the wet grout to create a consistent depth that shows the relief of the stone edges.
    • Full Joint: Does not have as much depth as a raked joint and not as full as an overgrout joint. The grout comes close to flush with the face of the stone.
    • Overgrout Joint: This is where the grout is flush with the surface of the wall and covers some parts of the stone. It makes the joints look bigger and the stone smaller.
    • Weep Joint: A weep joint is where the grout is used in excess between the stone and is left on the face of the stone. This technique is intensely rustic looking. The grout drips and oozes from the joints.
    • Bead Joint: This joint is when the grout fills the joints completely and actually extends beyond the face of the stone. It is shaped into a mound that surrounds each stone.
    • Grapevine Joint: Similar to a Full or Raked joint except before the grout sets up, a sharp tool is dragged through the center of each joint. This creates an outlined effect in the grout.
  9. Finishing the wall. If you are completing a dry stack look, as the mortar sets up you can remove any chinks or shims that you do not want to see. Clean any excess mortar or grout from the surface of the stone. You may have to use a wire brush to accomplish this.

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Project Options

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Maintenance

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The Fine Print

Please be aware that each project is unique and may pose different obstacles and circumstances that this guide cannot foresee. It is intended as a reference only. Most of these installation techniques are great for our geographic location here in Atlanta, GA. Soil conditions and climate play a large role in how each project is constructed. For example, if you live in the Northeast you will have to use a deeper base material to account for the freeze/thaw cycle that is notorious for upheaving patios. Stone Forest cannot be held liable for any damages incurred by the use of this guide.

Please seek a professional contractor’s advice if you are uncomfortable with undertaking a project you have not completed before.

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